Radio receiver



Aug. 17, 1943. E. F. ANDREWS RADIO RECEIVER 8 Sheets-Sheet 1 Filed May 24, 1959 1943- I E. F. ANDREWS 2,326,737

RADIO RECEIVER Filed May 24, 1939 8 Sheets-Sheet 2 8- 1943. E. F. ANDREWS 2,326,737

RADIO RECEIVER Filed May 24, 1939 8 sheets sheet 5 Aug. 17, 1943. ND WS 2,326,737

RADIO RECEIVER 8 Sheets-Sheet 4 Fil ed May 24. 1939 Au \7 1943. E. F. ANDREWS RADIO RECEIVER Filed May 24, 1939 8 Sheets-Sheet 5 672% mfamw,

RADIO RECEIVER Filed May 24, 1939 8 Sheets-Sheet 6 imam 0a. gaam amew4 Qg wyk aw Aug. 17, 1.943.

E. F; ANDREWS RADIO RECEIVER Filed May 24, 1939 8 Sheets-Sheet 7 Aug. 17, 1943. E F, ANDREWS 2,326,737

RADIO RECEIVER Filed May 24, 1959 8 Sheets-Sheet 8 "Patented Aug. 17, 1943 UNITED STATES PATENT OFFICE.

RADIO RECEIVER Edward Andrews, Chicago, Ill. Application May 24, 1939, Serial No. 275,431

21 Claims.

- and adapted automatically to effect the quick stoppage of .the tuning means when the receiver has been tuned to the carrier wave of a broadcasting station received with sufiicient strength.

The manually actuated means suitably comprises means controlling the change of an electric current or voltage, and may be located at a point remote from the receiver, from which point control maybe effected by means of a simple cable, or by other communicating means.

One of the objects of the present invention is to provide an improved radio receiver of this pe. Y

A further object of the invention is to provide means whereby the efiect of static and other undesired electrical disturbances are minimized or prevented, thus avoiding automatic stoppage where there is no desired signal.

- A further object of the invention is to provide in a radio receiver of this type improved volume control means which may be operated at any desired distance from thereceiver.

A further object of the invention is to provide an improved mechanism whereby the tuning device maybe arrested more precisely at positions of more exact resonance.

A further object of the invention is to provide means whereby the characteristics of antomatic volume control in a receiver of this type may be automatically adapted to the requirements. of stop-on-carrier tuning during tuning and again automatically adapted to the requirements for normal reception after the tuning has been effected.

A further object is to provide a receiver of this type in which the sensitivity of the automatic tuning-means may be readily controlled (froma v remote point, if desired), whereby thes et can be adapted for tuning in a relatively small number of the strongest stations or a greater number of stations, including distant stations, the signals from .which are comparatively weak.

A further object of this inventionjs to provide a receiver of this type with means whereby the tuning vector is caused to turn the tuning means for a minimum length of time or for a minimum distance before automatic stoppa e can occur after the actuation of the starting device.

A further object of the invention is to provide an improved mechanism for operating the tuning device and the volume control device at properly reduced speeds from the same electric,

motor.

A further object of the invention is to produce an improved type of sto-p-on-carrier stepping relay.

' A further object of the invention is the provision of an improved mechanism'ior reducing the effect of inertia and energy of rotation to efiect quicker stoppage.

A further object of the invention is to provide improved means for securing the greatest auto matic control of the set with a small number of simple controls.

A further object of the invention is to provide an improved automobile radio set and an improved installation thereof in an automobile.

A further object of the invention is the provision of a mechanism for adapting the stop-oncarrier mechanism for operation on widely different frequency bands.

A further objectof the invention is the provision of illuminated indicating means for indicating the condition of sensitivity, and if desired, the direction of rotation of the motor opcrating the tuning means and volume control means.

Certain features of the present invention are disclosed and claimed in my copending divisional application, Serial No. 403,094, filed July 19, 1941. 1,

Other objects, advantageaand capabilities oi the invention will appear from the following description of preferred embodiments thereof, taken in conjunction with the accompanying drawings, in which Fig. 1 is a wiring diagram of a radio receiver embodying the invention and intended primarily for alternating current operation in the home; i v i Fig. 2 is a similar diagram of a radio receiver embodying my invention and intended primarily for operation in an automobile from the automobile storage battery;

of the radio receiver shown insFig. 1;

Fig. 4 is a fragmentary sectional detail, the section being taken on theline 4-4 oi Fig. 3;

Fig.5 is a fragmentary section on a larger scale, the section being taken on the line 5-5 of Fig. 3;

Fig. 6 is an elevational detail showing a modi fled form of operating means for the reversing switch;

Fig. 7 is a front elevational view of an indicator dial which may be employed in radio receiving sets embodying my invention;

Fig. 8 is a fragmentary sectional detail view therethrough, the section being taken on the line 8-8 of Fig. 7:

Fig. 9 is a perspective view of a station indicating tab which may be employed in connection with the dial shown in Figs. 7 and 8;

Fig. 10 is a diagrammatic viewshowing the manner in which the receiver illustrated in Fig. 2 may be mounted in an automobile; Fig. 11 is a fragmentary sectional view of one end of the receiver shown in Fig. 10 showing the relative relation of certain of the control elements of the receiver;

Fig. 12 is a sectional detail view therethrough, the section being taken on the line |2-|2 oi Fig. '11;

Fig. 13 is a sectional detail view therethrough, the section being taken on the line |3-|3 of Fig.

I 11 and illustratingthe construction of the stopon-carrier clutch-brake relay embodied in the receiver;

Fig. 14 is a fragmentary elevational view or another form of stop-on-carrierclutch-brake relay which may advantageously be employed in either of the embodiments of the invention;

Fig. 15 is a fragmentary sectional elevation therethrough on a larger scale, the section being taken on the line |5-| 5 of Fig. 14;

Fig,'16 is a section detail taken on the line |6-|6 01' Fig. 15;

Fig. 17 is a wiring diagram of an automatic control system embodying "my invention, similar to that of Fig. 1;

Fig. 18 is a fragmentary front elevation showing part of the tuning and volume control mechahism mounted on a chassis;

Fig. 19 is a side elevation and partial cross sectional view of Fig. 18;

Fig. 20 is a fragmentary wiring diagram showing certain modifications which may be made in the wiring diagram of Fig. 1; and

Fig. 21. is a similar fragmentary wiring diagram showing further modifications which may beincorporated in this wiring diagram.

Referring to the drawings and particularly to Fig. 1, th 'radio s'et illustrated therein is a superheterodyneset comprising an antenna circuit 20,

a radio frequency tube 2|, and oscillator and demodulator tube 22, intermediate frequency tubes 23 and 24, a diode detector and first audio tube 25, and a power tube 26 which is connected to a loud speaker (not shown) in known manner.

Tube 2| may suitably be a 6K7 tube, the tube 22,.

a 6A8 tube, tubes 23 and 24, 6K7 tubes, andtubes and 25 a GQTG and a 6L6G tube, respectively. The tubes 2|, 22, 23, 24 and'25 are coupled together in cascade by transformers 21, 28, 29, and' 30. Th output of the tube coupled through a condenser 3| power tube 26. 32, 33 and 34,

25 is resistance to the grid of the The set is tuned by condensers which are connected together in a gang, as indicated by the dotted lines '35. These I switch is physically united of the transtorm'er 55 is grounded. The

the grid of the stop-on-carrier triode 39. The

other end of the winding 31 is connected to oneend of the secondary of the transformer 30, which is connected through resistor 4|, resistor 42, and resistor 43 to groundand to the cathode of the rectifier elements of the tube 25. The connected ends of the winding 37 and of the secondary oi the transformer 30 are by-passed through condenser 40. The, other end 01' the secondary or the transformer 30 is connected to the diode plates of the tube 25. The triode 39 may be so biased as to draw plate current at all times and to produce a sharp rise in its plate current, as the alternating currentsignal in the coil 31 impressed on its grid substantially exceeds the negative bias, also impressed on its grid, irom the diode plate of the tube 25. This sharp rise in plate current produces a voltage across a resistance in the oathode circuit which constitutes the stop-on-carrier signal. The resistances 42 and 43 are paralleled by a condenser 44 and 'the winding '45 of a potentiometer which, together with the slider 46, constitutes the volume control oi the set. The slider 45 isconnected through a condenser 41 to the gridvof the triode elements of the tube 25. The condenser 41 and said grid are connected" through resistances 48, 49, and 5D to ground.

The grid of the tube 26 is connected to ground through a resistance 5| and to a contact 52 of a relay 53.

Power is supplied to the set by means of power leads 54, which are connected through the primaries ot'transiormers 55 and 56. A'secondary 57 of the transformer 56 supplies current for the filaments of the various tubes, as indicated. Another secondary 58 is connected tosupply heating current to the cathode of the full-wave rectifier 59, the plates of which rectifier are connected to a third high voltage center-tapped secondary ill rupted by a switch 54. which is located between the primaries of the transformers 55 and 55. This to a switch so that they open and close simultaneously. One side of the switch 65 is connected to the pole of a switch 56. The other side is tact ll! of a relay 53.

One side oi the secondary of the, transformer ductor 10.

55 is also connected through the winding of the relay 68 to a conductor H. The conductors 10 and 1|, together with a third conductor 12,- constitute a cable 13 of any desired length. This cable may beconnected'to any desired number of remote control units 14, two of which are shown by way of example in Fig. 1. It is, of course, to be understood that the comprises a winding 31 This winding is sharply tuned by connected to con-- cable 13 may comprise as many units 14 and as many branches as may be desired. Each unit 14 comprises three switches 15. 16, and 11, one side of each switch being grounded to the conduotor 12. The other side of the switch 11 is connected to the conductor 1|. The other side of the switch 16 is connected directly to the conductor 10. The other side of the switch 15 is connected through a resistance 18 to the conductor 10. It will readily be understood that when the switch 11 is closed, the electro-magnet of the relay 68 is energized and the pole of the relay 68 moves away from engagement with the contact 61 and into engagement with the contact 19. The contact 19 is connected to one of the poles 80 of the relay 69. The relay 69 includes a second 'pole 8i which is normally maintained out of engagement with a groundedscontact 82 by a hook-like projection 83 on the armature.

When the relay 69 is energized, the armature is moved so as to allow the contact 8| to become grounded, and the projection 83 moves the armature 80 out of engagement with the contact 84 and into engagement with the contact 85. The contact 84 is connected to a contact 86 of a switch 81. The contact 85 is connected to a contact 88 ofthe swith 89, to a'contact 90 of the switch 81,

and also to windings 9| and 92 of the motor 36.

A contact 930i the switch 89 is connected through the windings 94 and 95 of the motor 36. The windings 92 and 95 are connected to the ungrounded side of the secondary of the transformer 55. The pole of the switch 81 is connected to the contact 96 of the switch 66. The other contact 91 of this switch is connected to the pole of the switch 89. The pole of the switch 58 is connected to one side of the switch 65. The other side of this switch is connected to the contact II1 of the relay 53. It will be understood that when the switch 66 is in engagement with contact 96, the motor 39 is controlled by the switch 81, and when the switch 66 engages the contact 91, the switch 89 controls the motor.

When the switch 15 is closed, the circuit through the relay 69 is completed through the resistance 18. Owing to the presence of this resistance, the energization of the relay 69 is somewhat limited and the responsive movement of the armature of this relay is limited by the engagement of aprojection 98 carried thereby with a ratchet wheel99. The ratchet wheel 99 is rigidl connected to a cam wheel I00, which en gages the pole IOI of a switch I 02.

When the control switch 16 is closed, the relay 69 is energized quite strongly, withthe result that the projection 98 engages the ratchet wheel 99 with suiificient force to turn it a distance corresponding to one tooth. When the switch 15 is closed, the cam wheel I is not affected, and only the contact 8| is grounded. When, however, the switch 16 is closed, not only are the poles 80 and 8| moved from their normal position, but the cam wheel I00 is rotated a distance corresponding to one tooth on the ratchet wheel 99. The pole IOI of the switch I02 is in engagement with one of the contacts I03, I04. It will be understood that each time the button 16 is pressed, the contact IOI is moved from one of the contacts I03, I 04 to the other one. The contact I04 is connected through an adjustable resistance I05 and a fixed resistance I06 to the cathod of the gas tube I01,

which may be an 884 tube or a gas tube known as R6071 or R. C. A. 2051. The contact I03 is connectedthrough a variable resistanc I08 to the fixed resistance I06. It will thus be seen that I29 of the reversible motor 36.

each movement ofthe cam wheel I00 merely results in the grounding of the cathode of the tube I01 and the resistance I06 through a variable resistance I05 or I08. Ordinarily, these last two resistances are set at considerably different values. Thus, if the resistance I05 is greater than the resistance I08, the set will have a lower sensitivity when connected through the resistance I05 than'it has when connected through the resistance I08. Consequently, the sensitivity of the set may be varied by pressing the button 16. Whenever either of the buttons 15 or 16 is pressed, th poles and BI are moved from their initial positions with results hereinafter to be more fully described.

The plate of the tube I01 is connected to the winding of the stop-on-carrier relay I09. This winding is connected in series with the winding of the relay 53 and through a suitable resistance I09 for limiting the steady current flowing through both relays from the B supply. The end of the winding of the relay I09 which connects to the winding of the relay 53 is also connected through a resistance III to the cathode of the tube I01, and this resistance is bridged by a condenser II2 adapted to supply a large surge of current through the relay I09 when the gas tube is ionized, the operation of which will hereinafter be more fully described.

The contact 01 of the relay 68 is connected to one of the poles II4 of the relay 53. The other pole II5,of this relay is grounded and is mechanically attached to the pole I I4 by a bar II6 of insulating material. When the relay 53 is energized, thearmature is moved downwardly, as viewed in Fig. 1, and thepole H4 is moved away from the contact II1, which connects to one pole of the switch 65. At the same time, the pole H5 is moved away from the contact 52 and is moved into engagement with the contact II8. This contact is connected to a condenser H9. The capacity of this condenser may, for example, be about 0.1 microfarad. When the switch 64 is open, that is, when the set is not operating, the armature of the relay 53 is biased towards the winding against the action of a spring I20 by a thermostat I2I. This is a strip of bi-metal which is provided with a heater coil I22 in parallel with the filaments with the result that after the filament current is turned on for a short time, the strip I2I becomes heated and moves away from the bar H6. The cathode of the tube 39 is connected through a choke coil I23, a switch I24, and resistance I25 to ground. The coil I23 and resistance I 25 are by-passed by a small radio frequency by-pass condenser I26. One side of the switch I24! and the adjacent side of the resistance I25 are connected to the grid of the tube I01. The switch I24 is actuated by .a minimum time device, two types of which will be described in connection with other figures.

The minimum time switch I 24' is best shown in Fig. 3. It may be operated by a weighted bell crank lever I21, which is pivotally mounted on a bracket I28 carried on the end of the shaft The motor 36 is mounted between two plates I30 and I3I, which may be mounted on the chassis of the receiver. One arm of the bell crank lever I 21 terminates in an engaging member I32 in alignment with the shaft I29. The engaging member I32 is normally biased by a spring I33 so as to open the'switch I24. When the motor 36 attains suflicient speed, the weighted end of stops, the spring I33 returns the lever I21 tothe position shown in Fig. 3, thereby opening the switch I24.

The gang of condensers 32, 33, and 34 are actuated by a common shaft upon which is mounted a drum I35. A cord I36 extends around the drum and around a split sleeve I31 upon which is mounted a manually operable knob I38. The split sleeve I31 has a frictional engagement with a shaft I39. The cord I36 extends around the sleeve I31 several .convolutions so that this sleeve is normally compressed against the shaft 139. 'Means (not shown) are provided for preventing the axial movement of the sleeve I31 'on the shaft I39. The shaft extends freely through a hub I40 of a gear I4I' and through bearings I42 and I43 on the plates I and I3I, respectively. The hub I is provided with a plurality of recesses I44, and the shaft I39 carries a pin I which is adapted to be introduced into one of the recesses I44 by merely pushing inwardly on the knob I38. The pin I45 may be disengaged from the hub I40by merely-pulling the knob I38 to its outermost position. The shaft I39 is provided with two grooves I46 which are adapted to receive a spring element I41,- so as to hold the shaft I39 in its inward or outward position, as the case may be. At its inner end, the shaft I39 carries a friction wheel I48. When the shaft I39-is in its outermost position, the friction wheel I48, which may have a peripheral portion or tire of rubber or the like, engages a shaft I49, which is also rotatably mounted on the plates I30 and I 3I. At its forward end, the shaft I49 carries a friction wheel I50 which is similar to" the friction wheel H8. The friction wheel I50 engages the hub I40 of the gear MI. The gear MI is connected through suitable speed reducing means, such as the gear and pinion I5| and I52 to a pinion I 53, which is adapted to be driven by the motor 36.

The :pinion I53 is shown on a large scale in Fig. 5. The pinion I53 is hollow and is slidably mounted on a sleeve I54 which extends inwardly towards the motor 36 from the core I55 of the relay I09. This relay is carried in front of the motor on the plate I30., with the sleeve I54 in axial alignment with the shaft of the 'motor." The pinion I53 carries at its outer end a disc I56 of magnetic material, which is adapted to be attracted by the relay I09 when its winding is an-axial recess\l60 in the core I 55. This spring applies pressure ona rod I6I which extends through the sleeve. I54 and abuts against a hardened disc I62, which is located within the hollow pinion I53 adjacent its innermost end.

The degree of compression exerted by the spring I59 is controlled by a screw I63. It will readily be understood that immediately the relay I09 is energized, the disc I56 is very strongly attracted and is moved to the left, as viewed in Fig. 5. The pinion I53 moves with it, and likewise the clutch projection I51. Consequently, these clutch members are withdrawn from the clutch ele-' ments I58, and the pinion I53 is completely freed of any connection with the motor 36. Owing to the small mass of the pinion I53 and the disc I56, this complete disengagement occurs very rapidly and the drive for the condenser is freed from the inertia of the motor armature. The magnetic force of the relay I 09 also draws the disc I56 strongly against the friction surface] I55, thus applying a strong braking action to effect the quick stoppage of the pinion I53. The elements of the drive between the condenser and the pinion I53 are driven relatively slowly and have small moments of inertia, so that their inertia is not aserious problem, as will hereinafter be more fully described.

When the knob I38 has been pressed inwardly, the shaft I39 is driven directly by the gear I4I through engagement of its hub I40 with the pin I45. This adjustment adapts the receiver for ordinary station reception. For short wave reception, it is preferred to adjust the drive of the gang of condensers so that it operates much more slowly. This object is obtainedby pulling the knob I38 outward, whereupon the drive of the condenser occurs from the gear I4I through its hub, the friction disc I50, its, shaft I49, and the friction disc I48.

The rear end of the motor shaft I29 is provided with a pinion I64 which is connected through speed reduction gearing I65 with a hub I66, which is rotatably mounted on a bearing I61. At its inner end the hub I66 carries a toothed wheel' I68. The toothed wheel 56 is adaptedto be, engaged by a pin I69, which projects rearwardly from a-detent wheel I10. The detent wheel I10 is carried on the rearward end of a hub I1I, this hub, being provided with a rigid abutment plate I12 which engages one side of the wheel I10, and a spring member I13 which resiliently forces the wheel I10 against the abutment plate I12. A shaft I14 extends through an opening I15 in the frame plate I30. The shaft I14 is held against axial movement by means of collars I16 rigidly mounted thereon on opposite sides of the plate I30.

-The hub I1I i provided with opposed slots I11 which receive opposite ends of a pin I18 rigidly mounted in the shaft :"I14. A pin I19 projects radially from the hub I H 50 as to cooperate with a cam member I80, which may suitably be formed from a rearwardly turned portion of the plate I30. The hub I1I is normally biased towards zero volume position of the volume control rheostat I8 I by means of a spring I82. This spring is anchored to a stationary abutment I83 and to the pin I19. The shaft I 14 extends freely through the hub I66 and carries at its innermost end one element I84 which cooperates with another element I 85 of a universal joint mechanism. The member 85 is mounted on the shaft I86 of the volume control rheostat I8I. This rheostat is supported by a bracket I81 from the frame member I3I. The frame member I3I supports the elements of the'relay 68,.p reviously referred to. .The armature of this relay is provided with a detent member I88 which is adapted to cooperate with the detent wheel I10. It will readily be understood that when the shaft I14 is manually actuated by the knob I89, the rheostat I8I is operated directly, the friction connection between the detent Wheel I10 and the hub I1I enabling this wheel to stand still in the position in which it is held by the detent I88. It will be understood that when the relay 68 is energized, the detent I88 is withdrawn from the wheel I10 and the spring I 82-throws the shaft I14 around to zero volume position. Furthermore, if the knob I 89 is rotated still further in the volume decrease direction, the switches 64 and 65, which are operated bythe rheostat shaft I86 are opened.

The friction connection between the wheel I 5 and the hub HI and the engagement of the wheel I10 by the detent I88 insures the maintenance of any manual adjustment, until changed by further turning of the knob I89 or the energization of the relay 68. It may here be remarked 10 that if the knob I89 is rotated in the opposite 5 direction by hand, the switches 64 and 65 will be opened. The volume control rheostat I 8I can, of course, be operated in either direction and the switches 64 and 65 turned on or off by the enerization of the relay 68 so that it moves its armature upwardly as shown in Fig. 3.

Upon the shaft of the gang of condensers I provide two arms I90 and I9I which are adapted to cooperate with the operatingarm I 92 of the switch 99. These arms come into contact with the arm I92 as the condenser shaft attains its extreme positions: The actuation of the switch 89 reverses the motor so that the same tends to operate in opposite directions while the condenser moves between extreme positions. In actual oporation, this backand forth movement is terminated when a station is tuned in which has suiiicient volume to energize the relay I09 and disconnect the motor. It is to be understood that the switch'81 and the switch 66 may be omitted, if desired, the switch 65 being connected directly to the pole of the switch 89. The switch 81 is preferably employed so as to enable a difierent adjustable range of tuning or range of condenser control between points of reversal to'be 40 employed. For this purpose. I loosely mount on the shaft I34 an arm I93. This arm is adapted to be engaged by two studs I94 and I95 which are adjustable to various positions in two arcuate slots I96 and I91 in a disc I98. This disc is rigidly mounted on the shaft I34. The arm I 93 carries a pin I99, which is located in a slot formed by the forked end of an actuating arm 200 of the switch 81. It will readily be understood that the position ,of the condenser at which the, arm 200 is actuated to reverse the motor can be controlled as desired by changing the position of the studs I94 and I95 on the disc I98. As has been previously described,the oscillation of the motor and the condenser maybe controlled by either switch 55.

81 or 89, control being transferred from one to the other by the mere actuation of the switch 66, which may be located at any desired position.

The dial 223 of the indicating device 238 is preferably translucent and carries suitable graduations and numbers which may correspond to the various frequencies of the broadcast band. The translucent dial 223 is illuminated by a plurality of lamps 224- on the. reverse side of the 5 dial. These lamps are mounted in a dish-shaped housing 225 which includes an annular shelf or flange 226 to which the periphery of the dial is secured in any. suitable way. Beyond .the

flange 226, the housing 225 is provided with an outer flange 221. ,This flange is displaced forwardly of the flange 226 so as to provide a space 228011 the outer side ofthe dial 223 in which the The pointer 229 tact with the window 23L placed portion 235 of the flange and the window ward face of the housing 225 is enclosed by a glass window 23I which is separated from the flange 221 by a gasket 232. The window- 23I is secured to the flange 221 by means of a securing ring 233, which includes an outer flange 234 adapted to be secured to the flange 221 by means of screws. The securing ring 233 is of step sec-. tion, as best seen in Fig. 8. It includes a flange 234 which is adapted to bear against the window 23I. The inner portion of the flange 234, which is indicated by the reference numeral 235, is displaced forwardly so that it is located out of con- Between the dis- 23I is provided a space 236 which is adapted to receive tabs 231. These tabs may be of transparent material, having a lighted background for opaque characters designating different broadcasting stations. The tabs 231 are preformed into concave shape as best seen in Fig. 9. To install a tab it is merely necessary to apply it to the glass 23I and slide it radially in the proper direction until its outer end is located in the recess" 236, as best shown in Fig. 8. The inner portion 235 of the flange 234 may be resilient and biased towards the window 23 I. As a result of the curvature of the tabs or the inward biasing of the portion 235, or both, the tabs 231 are firmly held in position. To adjust the position of a tab for a particular broadcasting station, it is only necessary to tune in that station and slide the tab circumferentially'so as to bring the opaque graduation at the inner end of the tab/in radial alignment with the pointer 229. The tabs may be removed when desired and they may be replaced by other tabs. Owing to the initial convex form of the tabs 231,

7 they lie quite flat against the window 23I when installed. It is of course to be understood that thewindow 23I is located in an opening in the front wall of the cabinet 239, which opening is finished bya suitable bezel 240.

The operation of this modification (as shown in Fig. 1) is as follows: a

The set is put into operation bypressing the button 11. This results in the energization of the relay 68 and the withdrawal of the detent I88 from the detent wheel I10. The pole II3 of the relay 68 is moved into engagement with the contact 19. The motor circuit is then completed from ground through the pole II3, contact 19,

pole of the relay 69, contact 84, motor windings,

94' and 95,,and secondary of the transformer 55 to ground. When the motor is thus put into operation, the pin I19 resting on the elevated surface of the cam I80, the pin I69 is engaged with the wheel. I68. Consequently, the motor drives the shaft I14 and consequently the shaft I86 in the volume increasing direction. The result of the initial movement of the shaft l86 in this direction results in the closing of the switches64 and 65'. The closure of thes'witch 64 immediately energizes the heater circuits, including the heating: element I22. Until the cathodes of the tubes are heated up, the thermostatic element I2I holds the poles of therelay 53 in their downward position, as shown in Fig.

l. The motor 36 operates as long as the button 11 is' pressed, and when the button 11 is released, the motor stops. When this occurs, the detent I88 withdraws the pin I69 from the wheel I68. The detent I88 locks the wheel L10 against rotation by the spring I82. The volume setting of the rheostat "I8I is thus maintained until the relay 68 is again energized. It will be understood that when the relay 68 is de-energized, operation of the motor will have no effect upon the volume control. Under these conditions, the motor will merely drive the condensers. When the heater I22 has raised the thermostatic ele ment I2I to a sufficient degree. of temperature, the pole II4 engages the contact H1, and the motor circuit is completed from ground through the pole II3, contact 61, pole II4, contact 1, switch 65, switch 66, one of the switches 81 or 89 (depending on the position of switch 66), through one of the pairs of field coils 9|, 92, or 94, 95 of the motor, and secondary of transformer 55 to ground. The motor will consequently start to operate in a direction depending upon the position of the switch 89 (or 81). 'Assuming that the switch'IiIi is in the relation shown in Fig. 1, the switch 89 will have control. It will be understood that if the switch 89 is in engagement with the contact 93, the motor will start to, move in the same direction as it did when the button 11 was first pressed. If, however, the switch 89 is in engagement with the contact 88, the motor will operate in the reverse direction. If no signal is being received by the set, the motor would continue to operate alternately in opposite directions, the arms I90 and I9I engaging the arm I92 of the switch 89 so as to reverse the motor for such operation.- When, however, a signal of adequate strength is received, ,the operation of the motor will be terminated in a manner which will now be described.

when a signal is received by the receiver, intermediate frequency energy is transferred from the primary of the transformer 30 to the winding 31. It may here be pointed out that if signals on closely adjacent frequencies are to be tuned stop-on-carrier, it is desirable that there be the maximum difference in amplitude between the desired signal and other signals on closely adjacent channels. It is therefore preferable that the intermediate frequency transformer 30 from which the stop-on-carrier signal .is obtained should be the last intermediate frequency transformer, that is, the one immediately ahead of the second detector. The coupling between the primary of the transformer and the winding 31 may be in the neighborhood of optimum coupling, or somewhat less. The coil 31 and the condenser 38 preferably form a high Q circuit sharply tuned to the intermediate frequency. An intermediate frequency signal in the tuned circuit of the coil 31 and condenser 38 is impressed upon the grid of the tube 39. The negative direct current voltage applied to the grid of the tube 39 is sufficiently high to cut off the broader base portion of the intermediate frequency signal in the tuned circuit 31, 38, so that the effective positive signal on the grid of the tube 39 is only as wide as that portion of the intermediate frequency signal which isof higher positive voltage than the negative voltage of the direct current signal. This produces an efiective signal on the grid of the tube 39 which is extremely sharp. The sharp-- ness of this signal is not substantially influenced by the coupling between the primary of the transformer 30 and the'coil 31, and can be best increased by increasing the Q of the tuned circult 81, 38. 'However, either, too tight or too loose a coupling will-undesirably affect the band passcharacteristics of the transformer 30 and therefore the quality of the audible signal. This coupling should therefore preferably beadjustd so that the resonance curve. has two peaks, with the single peak of the resonance curve of the through the resistor 18.

"should have a ratio of around 3 to 2 compared to the negative direct current voltage applied to the same grid from the diode element of the tube 25. When the sharp, positive intermediate frequency signal is impressed upon the grid of the tube 39, the current in the plate circuit of the tube 39 increases sharply. This plate current flows from the cathode of the tube 39 through the choke coil I23, the switch I24, and the resistance I25 to ground. The ungrounded end of the resistor I25 is connected to the grid of the tube I01. The condenser I26 serves as a high frequency by-pass condenser. The choke coil I23 serves as an anti-static choke coiLwhich is effective in greatly reducing the tendency of brief pulses, such as static, to ionize the gas tube I01. Sudden surges, such as static, have a short duration, and the choke coil I23, the resistance I25,

and the condenser I24 constitute a low-pass filter which blocks rapid impulses of brief duration. At the same time, this filter passes sustained oscillations of longer duration or lower frequency which create a substantial voltage across the resistor I25 when a station of suitable strength is tuned in. This voltage being applied to the grid of the tube I01 ionizes this gas tube, with the'result that the relay I09 is energized. This energization results in the immediate arrestment of the gang of condensers and the breaking of the motor circuit which occurs when the relay 53 is energized and the pole I II is withdrawn from the contact I I1. The condenser H2 is normally charged, owing to the voltage across the resistor III.

that a very large current flows through the winding of the relay I09'at the instant the plate current starts. Thus the condenser [I2 materially aids in the instant arrestment of the condenser.

It will be understood that when the gang condensers are thus arrested and the set is receiving a station, the relays 53 and I09 remain energized, due tothe fact that the tube'I01 remains in an ionized condition. When it is desired to tune? in another station, the button 15 is pressed. The result is that the relay 09 is energized.

For the reasons previously described, this energization of the relay 89 does notaffect the position of the ratchet wheel 99 and the cam wheel I00. The movement of the armature is, however, sumcient to bring the pole 8I into engagement with the pole 82, thereby grounding the grid of the tube I01. This de-ionizes and terminates the plate current of the tube I01, and the relays 53 and I09 are deenergized. The pole IIl moves upwardly into engagement with the contact H1 and thereupon the motor circuit is complete through the grounded pole II3,"'contact 51, pole II 4, contact II 1, switch 55, switch 55, and one or the other of the switches 81 or 89. Consequently, the motor operates until a new station is tuned in in the manner described above. If the button 15 is held depressed, the motor'continue's to operate the condensers until the button 15 is released. If the button 15 is depressed, the same action occurs as has just been described in connection with the button 15. In this case, however, the energization ofthe relay 59 is much stronger,

When the tube I01 is ionized, the condenser H2 is discharged, with the result carry the shaft .shaft I88 is attained,

and the cam wheel I is The net result is "that the grounded pole IOI is moved into engagement with the other contact I03 or I05. Consequently, the bias of the oathode of the tube II31 is altered and a different voltage is required on the grid of the tube I01 in order to initiate its operation. Thus, if the eiiective resistance I05 is larger than the effective resistance I08, thenv when the former is grounded through the pole IOI, it will require a higher voltage on the grid of the tube I01 to put this tube into operation by effecting its ionization than when the resistance I08 is grounded. Consequently, when the resistor I05 is effective, the set is adapted to respond to a smaller number or stations giving the strongest signals, and th resistor I08 responds to a larger number of stations, which includes stations giv ing weaker signals.

When the button 11 and the button 16 are depressed, then the relays 68 and 89 are both energized and the motor circuit is completed through the grounded pole II3, contact 19, pole 80, contact 85, windings 9| and 92, and secondary of transformer 55 to ground. Owing tothe energization of the relay I38, the detent I88 will be withdrawn from the ratchet wheel I10. The spring I82 is now free to rotate the hub I1I to zero volume position, which results in its axial movement, owing to the engagement of the pin I19 with themost elevated portion of the cam I08. This axial movement brings the pin I60 into engagement with the gear I68. The simultaneous energization of the windings 9| and 92 effects the drive of the motor in a direction to I86 beyond zero volume position in the volume reducing direction, opening the svwltches I54 and 65. If the buttons [6 and 11 are held depressed after-the final position of the the detent wheel I merely slips on the hub I1 I. When the buttons are released, the relays 68 and 69 are de-energized and the motor circuits are broken.

It may here be remarked that the minimum time switch I24 insures the movement of the condensers from one tuning position to another upon the depression of it were not for this switch, the buttons 15 o'r-15 might be depressed for a very short time and the gas tube I01 might be ionized again by the voltage derived The centrifugal means which controls the switch I24 insures sufiicient rotation for the condensers to tune out one carrier before they can be arrested by the gas tube I01, no matter how quickly the button 15 or 16 is actuated. h r

When the setis in operation, the depress'on results in the energization of the elevation of the detent I88 from the detent wheel I10; When this-happens, the spring I82 returns the shaft I14 and shaft I86 to zero volume control position of the rh'eostat IN, The cam I80 eifects the axial movement of the hub I1I so as to engage the pin I89 with the gear I68. The energization of the relay 68 causes the motor circuit to be completed through the windings operation in a direction to rotate the shaft I86 to increase the volume of the audible signal. During this operation of the motor, the tuning is unafiected because the relay main energized. When the button is released, the desired volume having been reached, the motor circuit is immediately broken, and-the detent the buttons 15 or 16. If

94 and 95 so that the motor is put into I00 and relay 53 removed one position.

1'0 with the contact 15 age, which 20 time the pacity of I88 engages and arrests the detent wheel I10 and moves it away from the gear wheel I68. The desired volume setting is maintained'by the en'- gagement of the detent I88 with the detent wheel I10 until the relay 68 is again energized. to be'noted that during normal reception, relay 53 is energized and the pole H5 is separated from the contact 52. When, however, the set is being-tuned, the pole H5 is in engagement 52, thus grounding the grid of the power tube 25 and muting the set. When the set is in normal reception, the condenser H9 is grounded through contact H8 and pole H5. Consequently, the automatic volume control voltis applied on the grids of the tubes 2I, 22 and 23 through theresistance relatively slowly due to'the time delay introduced by the resistance 20I and the capacity of the condenser I I9. During tuning, however, at which relay 53 is deenergized, the ground connection of the condenser II9 is'broken, with the result that the automatic volume control applied to the tubes just mentioned is substantially instantaneous, owing to the elimination of the cathe condenser I prefer to call fast automatic volume control. This fast automatic volume control during tuning has several very remarkable advantages. In the first place, owing to its almost instantaneous effect, it

3'0 demodulates received signals to' a considerable 10 station close to from the station which it was desired to tune out.

main portion of the set 201 "may tween the maximum and minimum amplitude of the carrier frequency resulting irom modulation. The result is that the signals are effective in 5 arresting the condensersr more on the average signal level of the carrier than on the peaks, due

to modulation. In the second place, fast automatic volume ccnirollargely eliminatesthe passing over of a weak station after leaving a strong it. Thus, if the condenser 'II9 weregroundcd during tuning; its charge might persist for scflicient time to prevent the stopping on a weak station, the frequency of which was close to that of the signal from a strong station, which had previously effected the'charging of the condenser. Finally, fast automatic volume control, owing to its practically instantaneous action, reduces the tendency of static or other undesired disturbances of brief duration 1) from stopping the condenser during tuning, Or-

dinary automatic volume control, notwithstanding itstime lag, may decrease the amplification of a relatively long or continuous signal to a high degree, while reducing amplification very little in the case of pulses having sharpwave fronts or peaks of very brief duration,

The radio set illustrated in Fig. 2 is intended primarily for an automobile receiver. In .general, the wiring diagram of the set is substantially similar to that illustrated in Fig. 1, with of one of the intermediate frethe omission quency tubes former 29. Consequently, corresponding fnume here have beengiven to similar parts. It may be noted, however, that the connections to the loud speaker 282 are shown in Fig. 2,while they are omitted in Fig. .1. The set comprises a vibrator 203 and associated transforming and rectifying means *20 adapted to provide the B supply for the tubes. Power is derived from a storage battery 205, which may be the battery of the automobile. As shown in Fig. 10, the loud speaker 202 may be located in the roof of an'automobile-206. The

be suitably lo- 20I, changes I9, providing what I- 23 and the corresponding transthe gas t potentiometer grounded arm 2 of a plurality of by the arm 2. The and thearm24l is, of

ment is particularly suitable for use with a. rod type antenna 208. Thus, the antenna may be mounted at the rear of the car and may be connected by a relatively short cable 209 to the set 201. The set 20'! may be supplied with electrical gas tube I01, which ha the eflect of deionizing be and lie-energizing the relays I09 and220 V On the common condenser shaft which Carries the rotors of the condensers I2, 23, and 34, I

slider oi a potentiometer 22I. potentiometer is grounded, the other being connected to the conductor 222. of the potentiometer 22! is connected to one terminal of the indicating device 2i2, which is a current responsive indicator graduated in the frequencies of the broadcasting band. It will thus be understood that while the slider 01' the 22l is located in the housing 2" of the automobile, the station to which the set is tuned is shown on the dial of the indicating means 2l2 on the dashboard.

.The sensitivity control device 2|! comprises a which isadapted to engage any contacts 242 on the dashboard.

course,-

srid bias of the tube In. The

' energized. when this 2,320,737 .cated in the hamper of the car. This arrangerelays. I09 and 220 are arranged in series in the plate circuit of the tube I01, as were the windings of the relays I09 and 53 in th previously described embodiment.

The relay 220 may be associated with a thermostatic element I 2i tion of the spring which is connected to its arma- The relay 220 comprises a pole 248 which by a switch 249 to a switch 250.

The two contacts 250 and by a high resista ce 255 which mutator ripple produced by the relay 220 includes a pole 251. The relay 220 also comprises a pole 258 which is connected through moved away from-the contact 26!, suit that fast automatic volume control is applied to these tubes. When the relay 220 is deenergized, the pole 251, which is ungrounded, engages a contact 262 which is connected to a cone grounding of the conductor 2S3 mute. When a station is tuned in, the relay I220 energizedand the muting circuit is broken. The pole 248 is adapted to engagethe rounded contact 204 when the relay 220 is de renders the set versed by the gang of condensers when the same arrives at an extreme position. Consequently, the condenser will be moved from one extreme position to the other continuously until a carrier is received with suflicient signal strength to energize the gas tube I01, whereupon the relays I09 and 220 are energized, arresting the movement of the condenser and breaking the motor circuit established between the pole 248 and the contact 264.

Thedevice just described with respect to Fig. 2 10 will be understood more fully in its physical embodiment, as shown in Figs. 10, 11, 12 and 13. The motor 36 is provided with a shaft 265 which carries a pinion 266 on its outer end. On the inner side of the pinion 266, the shaft 265 is pro- 15 The Dll'liOIi slight axial movement in alignment with the gear 210. 'I'hepinion 213 is quite similar to the pinion I53 shown in Fig. 5, Which pinion is actuated by the relay I09 in the manner described above in connection with the first embodiment.

It: is to be noted, however, that the relay I09 is located at an intermediate point of the gear train, which gear train comprises the elements 266, 210, 213, 2.14, 215, and 216, which is mounted on the shaft 211, which carries the gang'of tuning condensers and the contact arm of the potentiometer 22I. The element 216 carries projections 219 which are adapted to codperatc with the arm 280 of the reversing switch 250, previously described.

The pinion 269 is connected through a train 40 p of gear elements 282', 283, 284, 285, and 286, to a shaft 289 of the volume control 290. The shaft 289 also controls two switches 241 and 249 mounted on the back of the volume control 290,

so that the set may be turned off by turning the volume control beyond the zero volume posi- I tion in the volume decreasing direction. The trainof gears 282 to 286 is adapted to be arrested in definite position by means of the relay 2l5. The armature 29! is normally pressed outwardly by means of a spring 292 so that its reduced outer end 293 is adapted to project between the spokes of the gear element284.

The operation of this embodiment is as follows: The two-way switch 2I5 is thrown to one side, for example, to the left, as viewed in Fig. 2, so as to complete a circuit from ground through the relay 2I5', conductor 294, switch 2l5, conductor 2I6, winding 254, conductor 246, and bat-- tery 205 to ground. This drives the shaft 289 in a direction to close the switches 241 and 249 and to increase the volume level. When the switch 2I5 is released, the motor is stopped. The battery now supplies current to the filaments through conductor 246, switch 241, and conductor 222. It may here be interposed that if the volume level is too high, it may be lowered by merely throwing the pole of the switch 2I5 into contact with the conductor 2", whereupon the motor is driven in the opposite direction until the volume level desired is attained. When the set is first turned on the thermostat I2I is cold and maintains the poles 251, 258, and 248. in the position they occupy when therelay 220 is eneractuated except by the switch H5, in which case the relay 2I5' is energized. When the relay 2I5 is energized and the motor circuit is completed, the projection 293 of the armature 29lof the relay 2I5' is withdrawn from the gear 284, andthe motor starting, the gear train 282 to 286 is effective fondriving the shaft 289. When the circuit of the motor through the volume control relay 2I5' is opened by releasing the switch 2I5, the de-energization of the relay permits the spring 292 to thrust the armature 29I outwardly so that its projection 293 engages and arrests the gear 284. At the same time, the motor is de-energized and the inertia of the armature is accommodated by the slippage of the shaft 265 relative to the pinion 269. The operation of the motor 36 changes the position of the gang of condensers and associated elements. If the gang of: condensers is left so that no carrier wave is being received with suificient strength to eiiect the ionization vof the gas tube I01, then the relays I09 and 220 are not ener- 'gized so that the clutch elements 2H and 212 are in cooperative relation. Consequently, the motor, when it starts, is adapted to drive the gang of condensers. The motor goes into operation to drive the condensers when the heater I22 has raised the temperature of the thermostatic element i2I adequately. The motor circuit is ,matic volume control is applied to the grids of the tubes 2i and 22. When the condensers tune in a carrier wave of sufiicient strength, the gas tube 101 is ionized and the relays I09 and 220 are energized. The energization of the relay I09 effects an immediate interruption of the drive of the gang of condensers, and the energization of the relay 226 interrupts the motor circuit and effects the grounding of the condenser 259. It will, of course, be understood that when the relay 220 is tie-energized, the set is muted through the engagement of the pole 251 with the contact 262. When the relay 220 is energized, the muting circuit is interrupted by the downward movement of the pole 251, as viewed in Fig. 2.

The set being now in condition to receive a station if one of the buttons2I8 is pressed in-v wardly, the-grid of the gas tube I01 is grounded and the tube is de-ionized. This grounding occurs through the volume control relay 2I5, but this relay is not actuated since only a negligible current flows. The de-energization of the relays I09 and 220 causes the motor to be put into operation and it remains in operation as long as the button 2I8 is pressed. When the button is released, the motor continues to operate until the condensers tune in a station of sufilcient signal strength to ionize the tube I01. This ionization is effected by a positive voltage applied to the grid of the tube through the switch I24, which is controlled by a governor or other timing device,

such for instance, as that described in connection with the previous embodiment.

I have found it to be advantageous to locate 0 the clutch elements-21l and 212, together, with the gized. Consequently, the motor cannot be control relay I09, at an intermediate point of the gear train between the motor pinion 266 and the gear 216 driving the gang of condensers. At thev low speed end of the trairiithe torque transmitted by the clutch is high, and the clutch. elements would require a larger amount of energy for quick disengagement. On the other hand, at the high speed end of the train, the torque is small but the energy of rotation of the clutch members which remain connected to the condensers after the clutch is disengaged is high. As a matter of fact, this energy of rotation increases with the square of the speed and tends to prolong the time be tween the disengagement of the clutch and the stoppage of the condenser. For quickest condenser stoppage with reasonable clutch operating forces, a location of the clutch at an intermediate point of the gear train is highly advantageous'. It is also desirable'to decrease as far as practical the energy of rotation of all the parts which remain connected to the condenser shaft 211 and rotate therewith after the clutch is disengaged. Thoseelements, such as the gear 218, which are disconnected from the condenser shaft 211, after disengagement do not contribute to the continued rotation of'the condenser; therefore their energy of rotation may be disregarded.

In Figs. 14, 15, and 16, I have shown a modifled clutch arrangement operated by the relay I99. In these figures, the gear 298 corresponds to the gear 214 of the last described embodiment and the gear 291 corresponds to the gear 210. The gear 298, which meshes with the gear 296) corresponds to the gear 213. The hub oi. the gear 291 carries one or more projections 98 which are adapted to be engaged .by an arm 300 rigidly carried on the end 30I of the shaft member 302. The end 30I is round and has a bearing 303 in a plate 304. The plate 304 is rigidly mounted upon and in spaced relation to a plate 305. The plate 305 is provided with a bearin 306 for the enlarged portion 301 of the shaft member 302. Between the enlarged portion 301 and the end portion 30l, the member 302 is provided with an intermediate portion 308 which is of non-round exterior shape. It may be square, as shown in Fig. 16, and it extends through a bore 309 of corresponding shape in the gear 298. The gear 298 is located betweenthe two plates 304 and 305, and the member 302 is freely movable within it in longitudinal direction. Between the plate 304 and the arm 300 a conical coil spring 3I0 is situated which urges the shaft member 302 normally to the right, as shown in Fig. 15, pressing the rounded end 30I against the flat center portion of the hub of the gear 291. It may here be noted that the gear 291, the member 302, and the pole of the relay I09 are in axial alignment. The end of the enlarged portion 301 of the member 302, that is. the end which is normally located adjacent the pole of the relay I09. carries a frustro-conical head 3I3 of magnetic material. This head flares outwardly from the enlarged portion 301 and terminates in a large flat face. thin at the periphery. located quite close to the pole of the relay I09, as shown in Fig. 15.

When the relay I09 is not energized, the elements just described have the relation shown in Fig. 15. The spring 3I0 forces the end portion of the shaft member 301 into contact with the hub of the gear 291. A friction washer 3| I made from material such as Bakelite surrounds the pole piece of the relay I09, projecting a few .thousandths of an inch beyond the face 3 I 2 of the pole piece. When the head 3I3 is attracted by the energization of the relay I09, it bears upon the surface of the washer 3| I and does not make contact with the pole face, remaining separated from the face 3I2 of the pole piece by a small air gap. The washer 3I I constitutes an effective braking surface against which the rotation of the head 3I3 of the shaft member 302 is effectively braked when the relay I09 is energized.

In this embodiment of the invention, part of the gear train of the tuning control is common to the gear train of the volume control, both trains including the motor pinion 266 and the gear 291. The pinion 332, which is integral with the gear 291, mesheswith a gear 383 mounted for free rotation on a stub shaft 384. Upon the shaft 384 is mounted a pinion 385 which is adapted to be moved on the shaft towards the gear 383. The gear 383 is provided with a plurality of projec tions 306 directed towards the side on which the pinion 309 is located. The adjacent end of the pinion 385 carries an arm 381 which is adapted to engage one of the pins 388 when the pinion 395 is moved to the left, as viewed in Fig. 14. This movement of the pinion 385 is effected by a rod 38I which abuts against a disc 388, rigidly mounted in the end of the pinion 385 remote from the gear 383. The rod 38I is mounted for axial movement in a support 389. The rod 38I is moved to the left, as viewed in Fig. 14, when the volume control relay 332 (Fig. 17) is energized. The relay 2I5 may also be adapted to operate the rod 38I when energized, if it is desired to employ the volume control clutch shown in Fig. 14 in connection with the embodiment of the invention illustrated in Figs. 11, 12, and 13.

In the embodiment of the invention illustrated in Fig. 17, which like Fig. 1, is adapted to operate from an alternating current supply, an intermediate frequency tube is indicated by the reference numeral 24. This tube is coupled through the transformer 30 to the diode detector and first audio frequency amplifying tube 25, the relation of the tubes being substantially similar to the relation of the corresponding tubes in Fig. 1. A winding 31, which is closely coupled to the tuned secondary of the transformer 30, is connected to the first grid of the double triode 320. The first plate circuit of the tube 320 includes a sharply tuned high Q circuit comprising a winding 32I and tuning condenser 322, by means of which the plate circuit is tuned sharply to the intermediate frequency. The winding 32I is coupled to a winding 323 which is connected to the second grid of the tube 320. The winding MI is also coupled to a regenerative coil 324, which is connected to the first cathode of the tube 320, and serves to feed back energy from the plate circuit to the grid circuit of the first triode element of the tube 320. The regenerative coil 324 is connected through a condenser 325 and adjustable rheostat 328 to ground. The rheostat 326 is adjusted to prevent oscillation while providing the desired regenerative feedback. The second set of triode elements of the tube 320 are analogous to the tube 39 of the first described embodiment. Regeneration is employed in this arrangement to increase the Q and therefore the selectivity of the stop-on-carrier tuned circuit. The double triode arrangement is employed to prevent coupling between the regenerative stop-on-carrier circuit from adversely influencing the by-pass characteristics of the transformer 30. A single triode, as shown for instance in Fig.

1,'may of course be employed with the control circuits of this embodiment of the invention. The cathode of this tube is connected to an inductance I23 and resistance I 25 to ground. The inductance I23, resistance I 25, and condensers I24 and I26 have the same relation and function in a similar manner to those of the previous embodiment. The inductance I23 and resistance I are connected to the grid of a gas tube I81. The power supply includes an auxiliary transformer 55 and a power transformer 56. The primary of the transformer 56 is controlled by a switch 54. This switch is physically connected to a switch 65 so that these switches open and close together and are mounted on and actuated by the volume control. These and the other elements of the power supply unit are similar to those of Fig. 1 and are indicated by the same reference numerals.

The set may include a remote control unit similar to that of the first described embodiment. This unit may comprise switches 15, 16. and 11. The switches may be connected to a common wire 12, which is adapted to be grounded through a switch 321. The other side of the switch 15 is connected to the other side of the switch 16 through a resistance 18. Said other side of the switch 16 is connected by a conductor 18 to a relay 328 and to a contact 329. The other side of the switch 11 is connected through a conductor H to a relay 332 and to a pole 333 of a double pole switch which includes a pole 334 mechanically connected to the pole 333. The exterior portions of the three conductors 16, 1!, and 12 may be formed into a cable and be connected to the set by means of a plug 335 which is adapted to be inserted in a receptacle 336. The remote control may be removed from the set by merely withdrawing the plug 335.

It will readily be understood that a plurality of units 14 may be employed, if desired, the corresponding elements being merely connected in parallel, as shown in Fig. 1.

The switch 321 is a single pole switch adapted in one position to connect the conductor 12 to ground. This switch is physically connected to the switch 336' which is adapted, when the switch 321 is open, to connect conductor 331 to contact 338 of the relay 328. One side of the secondary of the transformer 55 is connected to the winding of the relay 332 and to the relay 328. One side of the switch 65 is connected to the pole 339 of relay 348. The other side of the switch 65 is connected to contact 34I of relay 332.

A switch pole 342, controlled manually by a button 343, is normally in engagement wi h a resilient contact 344. When the button 343 is pressed inwardly, the pole 342 is moved away from the contact 344. When, however. the butt0n343 is pulled outwardly, that is. downwardly, as viewed in Fig. 1'1, the contact 344 is brought into engagement with the contact 329. The contact 344 is connected to a pole 345 which is normally in engagement with the contact 338. When the relay 328 is energized, the pole 345 moves away from the contact 333. The pole 342 is connected to a contact 345 which is normally engaged by the manually operable t\vo way switch pole 341. The switch pole 341 is maintained in neutral position. as shown in Fig. 1'1, by means of springs 348. The switch pole 341 is grounded. When the switch pole 341 is thrown in one direction, it is brought into engagement with the contact 349, which is connected to the contact 358. associated with the pole 333. When. however, the switch pole 341 is thrown in the other direction, it is brought into engagement with contact 35l, which is connected to a contact 352, also associated with the pole 333. The contacts 338 are also connected to contacts 358 and 352. An

arm 33I, moving with the shaft of the gang of condensers, from which it is insulated, is adapted to engage contacts 338 at each end of the condenser travel, automatically reversing the direction of the condenser travel. The arm 33I is connected through a switch 458 to a contact 45!, which is normally engaged by the grounded pole 368. The switch 458 is mechanically connected to the switches 64 and 65 so that the contacts 338 cannot be grounded when the relay 332 is energized or the switches 64 and 65 are open. The secondary of the transformer 55 is connected to both windings 353 and 354 of the reversible motor 36 which actuates the tuning condensers and also the volume control. The windings 353 are connected to a contact 355 on one side of the pole 334. The windings 354 are connected to a contact 356 on the other side of the pole 334. The armature of the relay 332 carries a finger 356 which is adapted to cooperate with a ratchet wheel 351. The ratchet wheel 351 is rigidly con nected to a cam wheel 353 which is provided with a series of alternating recesses and projections. The cam wheel is adapted to cooperate with a cam member 359 carried by the pole 334. Each time the relay 332 is energized, the cam wheel 358 is tuned one step, moving the projection 359 from a hump on the cam wheel into a recess on the cam wheel, or vice versa. Consequently, the poles 333 and 334 are moved alternately from a position in which they engage the contacts 358 and 355, respectively, to another position in which they engage the contacts 352 and 356, respectively, and vice versa. On each energization of the relay 332, the pole 368 engages the contact 34I and may immediately separate therefrom. The armature of the relay 328 is provided with a projection 36I which is adapted to engage a ratchet wheel 362 in the same manner as the projection 358' 'engages the ratchet wheel 351. The ratchet wheel 362 is rigidly connected to a cam wheel 363 which is similar to the cam wheel 358. This cam wheel cooperates with a projection 364 on a pole 365. The pole 365 is rigidly connected to a pole 366. When the projection 364 is received in a recess in the cam wheel 363. the pole 383 engages a contact 361. which contact is connected to an incandescent lamp 368. The other side of the incandescent lamp and the pole 366 are connected to the filament supply, and it will readily be understood that when the cam wheel 363 is in the position in which it is shown in Fig. 11, the lamp 368 is illuminated. It shines through a window 369 which may include a layer of translucent material 318. This material may, for example, be white Celluloid. On the rear side of the sheet 316 is a layer of colored material 31L which may be red. This layer carries. suitably in black or in letters of a contrasting and preferably opaque color, a suitable ind cating legend, such as the word distant. On the front of the layer 318 is carried another suitable legend, such as the word local. This legend should be translucentand have the same color as the layer 31I, namely red. It will readily be understood that when the lamp 368 is lit. the legend distant appears to the observer. thelegend local being obscured by the general background of the same color. When. however. the lamp 366 is not lit, the rear legend distant" is not seen, and only the front legend, for example, local is seen by the observer.

The gas tube I81 has associated with it resistances I85, I86, I88, and III, and condenser H2. in the same relation as described in connection I VUIII with the first described embodiment. The resistance I05 is adapted to be grounded in one position of the cam wheel 353 through contact 312. pole 355, contact 338, pole 345. contact 344v pole 342, contact 346, and pole 341. When the cam wheel 353 occupies its other position, that is, the position shown in Fig. 17, the resistance I08 is grounded through contact 313, pole 365, and other connections, as before. It is to be noted that one or other of these two resistances is grounded at all times except when the relay 323 is energized, or when the button 343 is pressed, or when the pole 341 is out of engagement with contact 340.

The pole 339 of the relay 340 is rigidly connected to the grounded pole 314. A thermostat 315 keeps the poles 339 and 314 in the positions they occupy when the relay 340 is energized. The thermostat 315 is controlled by a heater winding 310 which is connected to the filament supply and is turned on when the switches 64 and 65 are closed. When the relay 340 is energized, the pole 339 is moved away from the grounded contact 311 and the pole 314 is moved into contact with the contact 318, which is connected to the automatic volume control delay condenser 310, which operates in the manner hereinbeiore described in connection with the corresponding condensers H9 and 259. At the same time, the pole 314 is moved away from the contact 380, making the signals audible which were muted during tuning in the manner hereinbefore described. Assuming that the switch 321 is connected to the conductor 12, that the switch 336' i opened, and that the cable 13 is connected to the set, then if the set is out of operation, the switches 54 and 05 are opened and only the transformer 55 is energized. The set is put into operation by pressing the button 11, whereupon a circuit is completed from ground through the switch 321, conductor 12, switch 11, conductor II, relay 332, and secondary of the transformer 55 to ground. The movement of the armature of the relay 332 moves the pole 300 into engagement with the contact 34I, thus completing a. circuit through the motor 36 and through one or other of the contacts 355 or 350 which is engaged by the pole 334. If the resulting rotation of the motor does not start the set. the button 11 is released and pressed again. This actuation results in changing the pole 334 into engagement with the proper contact to start the set. When the relay 332 i energized, the clutch for the volume control is put into engagement by the rod 38I and consequently the operation of the motor in the proper direction closes the switches 53 and 65 and continues to turn the volume control in the direction to increase volume as lon as the button 11 is pressed. The button is released as oon as the switches 64 and 65 are closed. Then, as soon as the filaments of the tubes are heated, the volume may be adjusted to the proper level. If. at any time, the volume level is too high, it can be lowered by merely pressing the button 11 again. If too low, the button 11 is again pushed. This actuation results in the fact that the pole 334 is moved to the right or to the left by the cam wheel 358 on each actuation of the button 11. The closure of the switch 64 results in the energization of the filament supply. Until the filaments heat up, the thermostat 315 holds the pole 339 out of engagement with the contact 311, and the motor cannot be put into operation except by the button 11. When the heater 316 has warmed the thermostat up, the pole 339 moves upwardly into engagement with the contact 311 if the set is not receiving a signal suilicient to maintain the tube I01 ionized. Consequently, the motor i put into operation in a. direction depending upon the position of the pole 334 until such a station is tuned in by the gang of condensers. Owing to the non-ionized state of the tube I01, the relay I09 is not energized. When a station is received with sufficient signal strength, the tube I 01 is ionized and the relays 340 and I09 are energized. The energization of the former open the motor circuit and the energization of the latter declutches the condenser drive and applies a brake. The tube I01 remains ionized while the station is being received. When the button 15 is pressed, a circuit is completed from ground through the resistance 18, the relay 328, and the secondary of the transformer 55 to ground. The encrgization. of the relay 328 moves the pole 345 away from the contact 338, thus breaking the circuit which connect resistance I05 or I08, depending upon the position of the pole 355, to ground. It will be readily understood that when this ground connection is broken. the voltage of the cathode of the tube I01 attains a high positive value corresponding to a high negative grid bias, the plate circuit. is broken, and the tube is de-ionized. The de-ionization oi the tube I01 causes the relay I00 to relax the brake and engage the clutch, and causes the relay 340 to complete the motor circuit. The direction of rotation of the motor depends upon the position of the pole 334. If it is desired to reverse this direction, it is merely necessary to close the switch 11 for the shortest possible time. This will have no appreciable eilect upon the volume level. It is here to be noted that the energization caused by the button 15 is insuflicicnt to cause actuation of the ratchet wheel 362. If the button 15 is depressed, it has the same effect as the button 15 as has just been described, with the addition that the cam 353 is moved one step and the circuit connecting the plate of the tube I01 to ground is changed from resistance I05 to resistance I08, or vice versa, changing the sensitivity of the stop on carrier tuning system. At the same time, the incandescent lamp 300 is either extinguished or lit, as the case may be.

The energization of th relay 332 displaces the rod 3BI which controls the volume control clutch in the manner described in connection with Fig. 14. During normal operation of the device, to change from station to station. it is merely necessary to push momentarily the button 15. When the condenser shaft I34 reaches the end of its travel in either direction, a circuit is completed through the relay 332 by the contact 33I, which moves with the condenser shaft 334, engaging one of the contacts 330, thereby producing the same effect as if the button 11 had been pressed momentarily. The result is that a circuit is completed through the relay 332 for a short time, which has the efiect of reversing the motor, the motor current being passed through the windings 353 or windings 354, depending upon the position of the pole 334. If it is desired to reverse the movement of the condenser shaft I34 at. any time, it is merely necessary to press momentarily the button 11. This changes the location of the pole 334. This enables a user to go back immediately to a station which he has just left. All he has to do is push the button 11 momentarily and then the button 15 momentarily. The rotation of the tuning condenser or other type of 

